U.S. patent application number 15/585769 was filed with the patent office on 2017-11-09 for transmission of magnetic resonance signals by differential cable routing.
The applicant listed for this patent is Stephan Biber, Jan Bollenbeck, Martin Hemmerlein. Invention is credited to Stephan Biber, Jan Bollenbeck, Martin Hemmerlein.
Application Number | 20170322267 15/585769 |
Document ID | / |
Family ID | 55913498 |
Filed Date | 2017-11-09 |
United States Patent
Application |
20170322267 |
Kind Code |
A1 |
Biber; Stephan ; et
al. |
November 9, 2017 |
TRANSMISSION OF MAGNETIC RESONANCE SIGNALS BY DIFFERENTIAL CABLE
ROUTING
Abstract
A transmission apparatus for transmitting an intermediate
frequency signal and an oscillator signal for mixing down the
intermediate frequency signal, a magnetic resonance tomograph with
a local coil, a receive unit, and a transmission apparatus are
provided. The transmission apparatus has a symmetrical transmission
line for transmission of the oscillator signal and the intermediate
frequency signal and a symmetrizing element for adaptation of an
unsymmetrical signal source and/or signal sink to the symmetrical
transmission line. The symmetrizing element has only ferrite-free
inductances. The local coil and the receive unit are connected for
signaling purposes via the transmission apparatus.
Inventors: |
Biber; Stephan; (Erlangen,
DE) ; Bollenbeck; Jan; (Eggolsheim, DE) ;
Hemmerlein; Martin; (Bamberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Biber; Stephan
Bollenbeck; Jan
Hemmerlein; Martin |
Erlangen
Eggolsheim
Bamberg |
|
DE
DE
DE |
|
|
Family ID: |
55913498 |
Appl. No.: |
15/585769 |
Filed: |
May 3, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 33/385 20130101;
G01R 33/3815 20130101; G01R 33/3621 20130101; H03H 7/42
20130101 |
International
Class: |
G01R 33/36 20060101
G01R033/36; G01R 33/385 20060101 G01R033/385; G01R 33/3815 20060101
G01R033/3815 |
Foreign Application Data
Date |
Code |
Application Number |
May 3, 2016 |
EP |
16168126 |
Claims
1. A transmission apparatus for transmitting an intermediate
frequency signal and an oscillator signal for mixing down of the
intermediate frequency signal, the transmission apparatus
comprising: a symmetrical transmission line for transmission of the
oscillator signal and the intermediate frequency signal; and a
symmetrizing element configured to adapt an unsymmetrical signal
source, a signal sink, or the unsymmetrical signal source and the
signal sink to the symmetrical transmission line, wherein the
symmetrizing element has only ferrite-free inductances.
2. The transmission apparatus of claim 1, wherein the oscillator
signal has a frequency greater than 50 MHz, and the intermediate
frequency signal has a frequency less than 20 MHz.
3. The transmission apparatus of claim 1, wherein the transmission
apparatus has a local attenuation minimum in a frequency range of
the oscillator signal and in a frequency range of the intermediate
frequency signal, respectively.
4. The transmission apparatus of claim 1, wherein the transmission
apparatus has a local maximum of a common mode rejection in a
frequency range of the oscillator signal and in a frequency range
of the intermediate frequency signal, respectively.
5. The transmission apparatus of claim 1, wherein the symmetrizing
element includes a Boucherot bridge.
6. The transmission apparatus of claim 5, wherein the Boucherot
bridge, in at least one branch of the Boucherot bridge, has two
stages.
7. The transmission apparatus of claim 5, wherein each capacitance
of one or more capacitances of the Boucherot bridge is replaced by
a respective parallel oscillating circuit, each inductance of one
or more inductances of the Boucherot bridge is replaced by a
respective series oscillating circuit, or a combination
thereof.
8. The transmission apparatus of claim 6, wherein each capacitance
of one or more capacitances of the Boucherot bridge is replaced by
a respective parallel oscillating circuit, each inductance of one
or more inductances of the Boucherot bridge is replaced by a
respective series oscillating circuit, or a combination
thereof.
9. A magnetic resonance tomograph comprising: a transmission
apparatus for transmitting an intermediate frequency signal and an
oscillator signal for mixing down of the intermediate frequency
signal, the transmission apparatus comprising: a symmetrical
transmission line for transmission of the oscillator signal and the
intermediate frequency signal; and a symmetrizing element
configured to adapt an unsymmetrical signal source, a signal sink,
or the unsymmetrical signal source and the signal sink to the
symmetrical transmission line, wherein the symmetrizing element has
only ferrite-free inductances; a local coil; and a receiver,
wherein the local coil is connected for signaling to the receiver
by the transmission apparatus for transmission of magnetic
resonance signals.
10. The magnetic resonance tomograph of claim 9, wherein the local
coil is connected to the transmission apparatus for signaling via
an asymmetrical interface.
11. The magnetic resonance tomograph of claim 9, wherein the
oscillator signal has a frequency greater than 50 MHz, and the
intermediate frequency signal has a frequency less than 20 MHz.
12. The magnetic resonance tomograph of claim 9, wherein the
transmission apparatus has a local attenuation minimum in a
frequency range of the oscillator signal and in a frequency range
of the intermediate frequency signal, respectively.
13. The magnetic resonance tomograph of claim 9, wherein the
transmission apparatus has a local maximum of a common mode
rejection in a frequency range of the oscillator signal and in a
frequency range of the intermediate frequency signal,
respectively.
14. The magnetic resonance tomograph of claim 9, wherein the
symmetrizing element includes a Boucherot bridge.
15. The magnetic resonance tomograph of claim 14, wherein the
Boucherot bridge, in at least one branch of the Boucherot bridge,
has two stages.
16. The magnetic resonance tomograph of claim 14, wherein each
capacitance of one or more capacitances of the Boucherot bridge is
replaced by a respective parallel oscillating circuit, each
inductance of one or more inductances of the Boucherot bridge is
replaced by a respective series oscillating circuit, or a
combination thereof.
17. The magnetic resonance tomograph of claim 15, wherein each
capacitance of one or more capacitances of the Boucherot bridge is
replaced by a respective parallel oscillating circuit, each
inductance of one or more inductances of the Boucherot bridge is
replaced by a respective series oscillating circuit, or a
combination thereof.
Description
[0001] This application claims the benefit of EP 16168126.7, filed
on May 3, 2016, which is hereby incorporated by reference in its
entirety.
BACKGROUND
[0002] The present embodiments relate to transmission of an
intermediate frequency signal and an oscillator signal for mixing
down the radio-frequency receive signal into an intermediate
frequency level.
[0003] Magnetic resonance tomographs are imaging apparatuses that,
for imaging an examination object, align nuclear spins of the
examination object with a strong external magnetic field and excite
the nuclear spins by a magnetic alternating field for precession
around this alignment. The precession or return of the spins from
this excited state into a state with lower energy generates a
magnetic alternating field as a response (e.g., a magnetic
resonance signal) that will be received via antennas.
[0004] With the aid of magnetic gradient fields, a spatial encoding
is impressed onto the signals, which subsequently makes it possible
to assign the received signal to a volume element. The received
signal is then evaluated, and a three-dimensional imaging
representation of the examination object is provided.
[0005] To excite the precession of the spins, magnetic alternating
fields with a frequency that corresponds to the Larmor frequency at
the respective static magnetic field strength and very high field
strengths or powers are to be provided. To improve the
signal-to-noise ratio of the magnetic resonance signal received by
the antennas, antennas that are often referred to as local coils
and are arranged directly on the patient may be used.
[0006] For imaging, the magnetic resonance signals received by the
local coil are transmitted to a receive device of the magnetic
resonance tomograph. The magnetic resonance signals may also be
stepped down by mixing the magnetic resonance signals into a lower
frequency range (e.g., intermediate frequency). In order to be able
to detect the phase and frequency features of the original magnetic
resonance signal during evaluation, the mixing signal or oscillator
signal is then likewise to be provided as a reference and is to be
transmitted.
[0007] The magnetic resonance signal may have a bandwidth of one
Megahertz. Once the magnetic resonance signal has been mixed down
to an intermediate frequency of, for example, 10 MHz, the
intermediate frequency signal consequently involves a relatively
wideband signal.
[0008] Coaxial cables that, in thin and flexible forms of
embodiment, for example, are expensive and difficult to work with
may be used for transmission of the signals.
[0009] The published patent DE 10104260 A1 discloses a symmetrizing
element for two frequencies. The published patent DE 102013209450
A1 describes a symmetrizing element for a widened frequency
range.
SUMMARY AND DESCRIPTION
[0010] The scope of the present invention is defined solely by the
appended claims and is not affected to any degree by the statements
within this summary.
[0011] The present embodiments may obviate one or more of the
drawbacks or limitations in the related art. For example, a
transmission apparatus and a magnetic resonance tomograph that are
easier to handle and are more cost-effective are provided.
[0012] The transmission apparatus is intended for transmission of
an intermediate frequency signal and an oscillator signal for
creating the intermediate frequency signal. The intermediate
frequency signal may therefore be provided in a frequency range
that is restricted upwards by a multiple of the magnetic resonance
signal bandwidth (e.g., by twice, three times, five times or ten
times the magnetic resonance signal bandwidth; is below 2, 5, 10 or
20 MHz). In this case, the oscillator signal is provided in a
frequency range around the Larmor frequency plus/minus the
intermediate frequency (e.g., above 50 MHz). For example, a
transmission apparatus of which the attenuation for the signals to
be transmitted is less than 3, 6 or 12 dB may be suitable for
transmission.
[0013] The transmission apparatus has a symmetrical transmission
line for transmission of the oscillator signal and the intermediate
frequency signal. A symmetrical transmission line is a transmission
line, in which, by contrast with an asymmetrical transmission line,
not one conductor of the at least two conductors has a reference or
ground potential. In a symmetrical transmission line, both
conductors of a conductor pair carry a signal (e.g., with opposite
polarity), so the emissions from the transmission lines or
radiations into the line cancel each other out. Symmetrical
transmission lines are referred to as differential transmission
lines. For example, the symmetrical transmission line may involve a
line with twisted pairs or a strip line or flat webbed line.
[0014] The transmission device has a symmetrizing element (e.g.,
balanced/unbalanced, "balun") for adapting an unsymmetrical signal
source and/or signal sink to the symmetrical transmission line. The
symmetrizing element has only ferrite-free inductances.
Ferrite-free inductances are, for example, air coils that do not
have any ferrite core, such as, for example, a ring core. The
transmission apparatus is differentiated in this way from
transmission devices that have a wideband symmetrizing element with
a ring core transformer as a balun.
[0015] The transmission apparatus may be used in an advantageous
manner in magnetic resonance apparatuses in an examination area,
since no ferrite saturation effects show up and disturb the static
and dynamic magnetic fields. In addition, the transmission
apparatus is capable of accepting signals from a normal local coil
with unsymmetrical signal output and transmitting the signals, even
if the signals lie in different frequency ranges for intermediate
frequency signals and oscillator signals.
[0016] The magnetic resonance tomograph shares the advantages of
the transmission apparatus.
[0017] In one embodiment of the transmission apparatus, the
transmission apparatus is intended for transmission of the
oscillator signal with a frequency of greater than 50 MHz and the
intermediate frequency signal with a frequency less than 20 MHz. In
this case, the bandwidth of the two signals may be less than or
equal to 1, 2, or 5 MHz. In one embodiment, the bandwidth of at
least the intermediate frequency signal is greater than or equal to
500 kHz or 1 MHz. The transmission apparatus may be suitable for
transmitting a frequency range if the attenuation in the frequency
ranges to be transmitted is less than 3 dB, 6 dB, or 12 dB.
[0018] The transmission apparatus is configured for equally good
transmission of signals in two frequency ranges lying far apart
from one another, as is to be provided for a magnetic resonance
tomograph with intermediate frequency.
[0019] In one embodiment of the transmission apparatus, the
transmission apparatus exhibits a local attenuation minimum in the
range of the frequency of the oscillator signal and in the range of
the frequency of the intermediate frequency signal, respectively. A
range may be the bandwidth of the respective signal or a multiple
thereof (e.g., twice, three times, or five times the
bandwidth).
[0020] A wideband adaptation of an unsymmetrical signal source to a
symmetrical transmission source is barely possible without
inductances with ferrites (e.g., ring cores, classical baluns). The
transmission apparatus provides an adaptation with low attenuation
in predetermined frequency ranges to be provided for the function
of the magnetic resonance tomograph.
[0021] In an embodiment of the transmission apparatus, the
transmission apparatus has a local maximum of the common mode
rejection for the frequency range of the oscillator signal and for
a frequency range of the intermediate frequency signal. A range of
1, 2, 5 or 10 MHz around the respective signal may be, for example,
the frequency range of the oscillator signal or the intermediate
frequency signal.
[0022] A common mode rejection specifies a measure for suppression
of faults that act on both wires of a symmetrical line. A maximum
of the common mode rejection in the range of the useful signals
reduces above all disturbances irradiated into the line (e.g.,
common mode faults) and improves image acquisition in this way.
[0023] In one embodiment of the transmission apparatus, this has a
Boucherot bridge as symmetrizing element. A Boucherot bridge refers
to a bridge circuit including at least two Boucherot elements, or a
low pass element and a high pass element in each case. The
Boucherot bridge converts at a rated frequency an unsymmetrical
line system into a symmetrical line system. In addition, the
interface impedances may be transformed in a narrowband system by a
Boucherot bridge, and power matching may thus be achieved.
[0024] At a rated frequency, a Boucherot bridge makes possible an
adaptation of radio-frequency signals even without ferrite coils or
transformers.
[0025] The classical Boucherot bridge has the serious disadvantage
that the function is merely able to be used in a single and also
relatively narrow frequency band around the rated frequency.
[0026] In one embodiment of the transmission apparatus, the
Boucherot bridge, in at least one or also in both branches, has two
stages. A stage refers to, for example, the respective Boucherot
elements (e.g., the high pass and low pass element) that are each
arranged in a branch of the Boucherot bridge. In the embodiment,
two low pass elements are connected in series in each case in a
branch of the Boucherot bridge and/or two high pass elements are
connected in series in each case in the other branch of the
Boucherot bridge. In this case, the two Boucherot elements
connected in series in each case differ in the values of
components, so that the two Boucherot elements have different
characteristic impedance curves.
[0027] The interaction of the two Boucherot elements with a
different frequency characteristic in one branch widens the
bandwidth of the branch of the Boucherot bridge in an advantageous
manner.
[0028] In one embodiment of the transmission apparatus, the
Boucherot bridge, instead of one or more capacitances, has a
parallel oscillating circuit in each case. Alternatively or
additionally, instead of one or more inductances, the Boucherot
bridge has a series oscillating circuit in each case. In one
embodiment, all capacitances of the Boucherot bridge are replaced
by parallel oscillating circuits, and all inductances of the
Boucherot bridge are replaced by inductances.
[0029] The oscillating circuits, through different resonant
frequencies, may allow the symmetrizing element to be optimized
simultaneously for different frequency ranges.
[0030] In one embodiment of the magnetic resonance tomograph, the
local coil is connected to the transmission apparatus for signaling
via an asymmetrical interface.
[0031] The magnetic resonance tomograph, through the symmetrizing
element of the transmission apparatus, may use a previously used
local coil with a connection for a coaxial cable in conjunction
with the low-cost transmission apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 shows an example of a schematic diagram of one
embodiment of a magnetic resonance tomograph;
[0033] FIG. 2 shows a schematic diagram of one embodiment of a
transmission apparatus with a local coil and a receive unit;
[0034] FIG. 3 shows a schematic diagram of one embodiment of a
transmission apparatus with a local coil and a receive unit;
[0035] FIG. 4 shows a schematic diagram of an example of a
symmetrizing element.
DETAILED DESCRIPTION
[0036] FIG. 1 shows a schematic diagram of a magnetic resonance
tomograph 1 with one embodiment of a transmission apparatus 70.
[0037] The magnet unit 10 has a field magnet 11 that creates a
static magnetic field BO for aligning nuclear spins of test samples
or in a body of a patient 40 in a recording area. The recording
area is arranged in a patient tunnel 16 that extends in a
longitudinal direction 2 through the magnet unit 10. The field
magnet 11 may involve a superconducting magnet that may provide
magnetic fields with a magnetic flux density of up to 3 Tesla, or
even more with the latest devices. For lower field strengths,
however, permanent magnets or electromagnets with
normally-conducting coils may be used.
[0038] The magnet unit 10 also has gradient coils 12 that, for
spatial differentiation of the acquired imaging regions in the
examination volume, are configured to superimpose on the magnetic
field BO variable magnetic fields in three spatial directions. The
gradient coils 12 may be coils made of normally-conducting wires
that may generate fields in the examination volume that are
orthogonal to one another.
[0039] The magnet unit 10 likewise has a body coil 14 configured to
irradiate a radio-frequency signal supplied via a signal line into
the examination volume and to receive resonance signals emitted by
the patient 40 and output the resonance signals via a signal line.
The magnetic resonance tomograph of one or more of the present
embodiments has one or more local coils 50 that are arranged in the
patient tunnel 16 close to the patient 40.
[0040] A control unit 20 (e.g., a controller) supplies the magnet
unit 10 with the various signals for the gradient coils 12 and the
body coil 14 and evaluates the received signals.
[0041] Thus, the control unit 20 has a gradient controller 21
configured to supply the gradient coils 12 with variable currents
via feed lines that are coordinated in timing to provide the
desired gradient fields in the examination volume.
[0042] The control unit 20 has a receive unit 22 (e.g., a receiver)
configured to create a radio-frequency pulse with a predetermined
timing curve, amplitude, and spectral power distribution to excite
a magnetic resonance of the nuclear spin in the patient 40. In this
case, pulse powers in the Kilowatt range are achieved. The
individual units are connected to one another via a signal bus
25.
[0043] The local coil 50 may receive a magnetic resonance signal
from the body of the patient 40, since because of the short
distance involved, the signal-to-noise ratio (SNR) of the local
coil 50 is better than receipt of the signal by the body coil 14.
The MR signal received by the local coil 50 are prepared in the
local coil 50 and forwarded by the transmission apparatus 70 to the
receive unit 22 of the magnetic resonance tomograph 1 for
evaluation and image acquisition.
[0044] FIG. 2 shows schematically an example of a transmission
apparatus 70 with the local coil 50 and the receive unit 22. In a
housing 51, the local coil 50 has an antenna coil 52 for receiving
an MR signal. The received MR signal will subsequently be amplified
by a pre-amplifier 53 (e.g., low noise amplifier, LNA). The MR
signal lies at the Larmor frequency, which is dependent on the
strength of the magnetic field BO and, for 3 Tesla, amounts to
around 130 MHz. The bandwidth of the MR signal amounts to around
0.5 MHz. The MR signal will therefore be mixed in a mixer 54 with a
signal of an oscillator 55 or an oscillator signal and converted
into an intermediate frequency signal for transmission at a lower
frequency. The intermediate frequency signal in this case, on
account of the simpler signaling technology, may be an asymmetrical
signal related to a signal ground.
[0045] In one embodiment, the oscillator signal may be created
locally, for example, in the local coil 50 by an oscillator 55. In
order to be able to re-establish the frequency and the phase
relationship of the MR signal during the image acquisition, the
oscillator signal may then also be transmitted from the local coil
50 to the receive unit 22 (e.g., via a common line or transmission
apparatus 70).
[0046] If a number of local coils 50 are provided on a magnetic
resonance tomograph 1, then in one embodiment, the oscillator 55
may provide the oscillator signal jointly for a number of local
coils 50 and the signal may be provided centrally in the receive
unit 22. The oscillator signal will then likewise be transmitted by
the transmission apparatus 70 between local coil 50 and receive
unit 22, but in the other direction. This form of embodiment is
shown in FIG. 3, which in other respects is no different from FIG.
2. The separation of the oscillator signal and the intermediate
frequency signal may be done, for example, by a high pass/low pass
combination (diplexer) in the local coil 50.
[0047] The transmission apparatus 70 has a symmetrizing element 71
that converts the asymmetrical intermediate frequency signal with
ground relationship into a symmetrical third signal without
potential relationship. Modified Boucherot bridges, which are
presented below, are suitable for converting the signals with
different frequency, for example. Classical baluns with ring core
transformers are not suitable, on account of the ferrites used, in
the environment of the field magnet 11.
[0048] The third signal is transmitted by a symmetrical
transmission line 72. A line of this type may be a twisted-pair
cable, for example, as is used for LAN cabling (e.g., referred to
as CAT4, CAT5 or CAT6) depending on screening and characteristics.
Plugs usual in LAN cabling, such as RJ-45, may also be employed.
However, other symmetrical lines such as flat webbed lines or strip
lines on flexible or rigid circuit board substrates may also be
provided. Other plug-in systems are likewise also able to be
used.
[0049] In one embodiment, the intermediate frequency signal may
initially be routed onwards on an asymmetrical transmission line
such as coaxial cable or asymmetrical strip lines from the local
coil to a transfer point. For example a possible application case
may be a spine coil integrated into a patient couch 40, of which
the intermediate frequency signals are conveyed to one end of the
patient couch 40 by an asymmetrical transmission line on a circuit
board substrate and may subsequently be adapted to a third signal
by a symmetrizing element 71 for further transmission on a
symmetrical transmission line 72. One or more of the present
embodiments include all these combinations of asymmetrical and
symmetrical transmission lines.
[0050] In one embodiment, a conversion of the third symmetrical
signal into an asymmetrical signal by a converter 73 again takes
place at the end of the symmetrical transmission line 72, since the
electronic signal processing in the receive unit 22 is mostly based
on ground-related, asymmetrical signals. If the transmission
apparatus 70 is transmitting the oscillator signal and the
intermediate frequency signal in the same direction, the converter
may be realized, for example, by a wideband differential amplifier.
A converter 73 with passive components that are realized, for
example, as in the symmetrizing element 71 with one or more
Boucherot bridges, is suitable for a transmission in both
directions.
[0051] In accordance with one or more of the present embodiments,
the symmetrizing element 71 of the transmission apparatus 70 may
also be arranged in the housing 51 of the local coil and/or the
converter 73 may be part of the receive unit 22 of the magnetic
resonance tomograph 1.
[0052] FIG. 4 specifies an example of a schematic diagram of a
symmetrizing element 71 of one embodiment of a transmission
apparatus.
[0053] The symmetrizing element 71, shown by way of example in FIG.
4, performs a conversion from a signal port with asymmetrical
signal and an impedance of 50 Ohm on the left-hand side, to a
symmetrical signal port with 100 Ohm impedance on the right-hand
side. Through the particular design of the symmetrizing element 71
shown, in the form of a "wideband dual-band Boucherot bridge," the
desired conversion takes place both in a frequency range of 55 MHz
to 75 MHz for the oscillator frequency and also in a frequency
range of 8 MHz to 12 MHz for the intermediate frequency signal.
[0054] A simplest form of design of a Boucherot bridge has an
asymmetrical signal input, to which two branches of the Boucherot
bridge will be fed. The branches correspond to the signal paths in
the upper or the lower halves of the circuit diagram in FIG. 4. A
differential or symmetrical output signal is present at the output
of the respective branches through phase shifting in the respective
branches in the opposite direction. Because of the passive
components, a signal flow in the reverse direction may also be
provided in order to convert a symmetrical signal into an
asymmetrical signal.
[0055] The opposing phase shift may, for example, be achieved by a
high pass in one branch and a low pass in the other branch. The
high pass and the low pass may also be referred to as Boucherot
elements. In FIG. 4, two such stages are connected in series in
each branch.
[0056] In addition, in the embodiment of FIG. 4, the capacitances
in the respective Boucherot elements are each configured as
parallel oscillating circuits and the inductances are each
configured as a series oscillating circuit. While low pass and high
pass each only obtain a phase displacement amounting to a maximum
of 90 degrees, oscillating circuits achieve a phase displacement
amounting to a maximum of 180 degrees, with 90 degrees at the
resonant frequency. Through suitable design of the resonant
frequencies, an oscillating circuit may thus act as a low pass at
one frequency and as a high pass at another frequency, so that the
Boucherot bridge with the oscillating circuits acts as a
symmetrizing element for two widely differing frequencies, by
changing the effect of the two branches.
[0057] A symmetrizing element 71 that, as shown in FIG. 4, is only
constructed from passive and ferrite-free components may be used in
the vicinity of the field magnet and is suitable for both
directions of the signal flow, from the symmetrical to the
unsymmetrical signal port and vice versa.
[0058] Although the invention has been illustrated and described in
greater detail by the exemplary embodiments, the invention is not
restricted by the disclosed examples. Other variations may be
derived herefrom by the person skilled in the art without departing
from the scope of protection of the invention.
[0059] The elements and features recited in the appended claims may
be combined in different ways to produce new claims that likewise
fall within the scope of the present invention. Thus, whereas the
dependent claims appended below depend from only a single
independent or dependent claim, it is to be understood that these
dependent claims may, alternatively, be made to depend in the
alternative from any preceding or following claim, whether
independent or dependent. Such new combinations are to be
understood as forming a part of the present specification.
[0060] While the present invention has been described above by
reference to various embodiments, it should be understood that many
changes and modifications can be made to the described embodiments.
It is therefore intended that the foregoing description be regarded
as illustrative rather than limiting, and that it be understood
that all equivalents and/or combinations of embodiments are
intended to be included in this description.
* * * * *